Cut butter into cubes and freeze for about 1 hour. In a bowl, whisk together flour, sugar and salt and chill in the refrigerator for about 30 minutes.
Add butter to flour mixture. Cut the butter into the flour using a pastry blender or by pinching the fat into the flour mixture with hands. Work them together until resembling coarse cornmeal with pea-like, butter-speckled pieces.
Slowly drizzle water to flour-butter mixture and with hands, mix until just combined. If the dough is too crumbly and does not hold together, add more water a tablespoon at a time. DO NOT ADD TOO MUCH LIQUID and DO NOT OVERWORK DOUGH.
Gently gather dough into a ball. Wrap with plastic wrap and chill in the refrigerator for about 2 hours.
Meanwhile, in a wide pan over medium heat, heat oil. Add onions and garlic and cook until softened.
Add ground beef and cook, breaking into pieces with the back of the spoon, for about 6 to 8 minutes, or until no longer pink.
Add tomato sauce and bring to a boil.
Add potatoes and carrots. Lower heat, cover, and simmer until meat is cooked. and vegetables are tender. Mixture should be saucy but not overly wet.
Add green peas and raisins. Continue to cook until vegetables are heated through and liquid is reduced. Season with salt and pepper to taste.
Transfer meat filling to a bowl and allow to cool completely.
Divide pie crust into 12 balls. Place each ball between two sheets of parchment paper and with a rolling pin, gently flatten each ball into 5-inch diameter and 1/4-inch thickness.
Using a round biscuit cutter or an inverted bowl, cut into the dough by gently twisting to form circles with smooth edges. Trim any excess dough.
On a flat work surface, lay dough circle and spoon about a heaping tablespoon of filling in the middle. Fold the bottom of the dough over filling and with fingers, press edges firmly. Using tines of a fork, press on sides of dough to firmly seal. Repeat with remaining dough and filling.
In a bowl, whisk together eggs, milk and salt.
On a lightly greased baking sheet, arrange prepared empanadas in a single layer and brush top with egg wash. Bake in a 375 F oven for about 25 to 30 minutes or until lightly browned.
Remove from oven and allow to slightly cool for about 1 to 2 minutes before removing from the baking sheet.